THE SOURCES AND USES OF IRON PYRITES. 
121 
the sulphuric acid of the sulphate of copper transfers itself to 
the iron with formation of soluble ferrous sulphate, while the 
'Copper, in a metallic granular state, but contaminated with the 
carbon and some other impurities of the pig iron, is deposited. In 
order to collect this precipitated copper, the liquors are diverted 
in succession from the various tanks forming portions of the 
arrangement for precipitation, the liquid drawn off, and the 
iron removed from one end of the tank, any adhering copper 
being brushed off. The copper in the bottom of the tank is 
now collected, and the cleaned iron replaced with an addition of 
fresh pig ; the operation being continued with the next stack in 
succession, until the whole of the pig iron has been cleaned 
and freshly stacked, and nearly the whole of the copper taken 
out. This precipitated copper, when washed, freed from frag- 
ments of iron, and calcined, contains about 75 per cent, of 
metallic copper ; it is then bagged and forwarded to England to 
be refined and melted into ingots, as the high price of fuel in 
Spain renders it inexpedient to complete its metallurgical treat- 
ment in that country. 
On account of the very limited rainfall which occurs in this 
portion of the Spanish peninsula, the supply of water requisite 
for these operations is exceedingly difficult to obtain, and it 
has consequently been found necessary to dam two large valleys 
by dykes, thus making reservoirs, of which one will be provided 
with powerful pumping machinery. The first of these tanks, 
which has for some time been in operation, is capable of con- 
taining 70,620,000 gallons of water, while the other, now in 
course of construction, will have a capacity of over 100,000,000 
gallons. 
All the engineering work connected with this vast under- 
taking has been skilfully designed and efficiently carried out 
by the resident manager, Mr. M. W. Carr, whose arrangements 
are already so far advanced that the production of copper from 
the extraction w 7 orks alone already exceeds 150 tons per week. 
The average number of work-people now employed upon the 
mines, railway, and calcination grounds of the Eio Tinto Com- 
pany, may be taken at about 5,000, but upon the completion of 
works in connection with the water supply, this number will be 
reduced, while the output of copper will be largely increased. 
The ores obtained from the different mines very closely re- 
semble one another in composition, but, as already stated, the 
richer, “selected,” ores only are exported for the use of the 
alkali manufacturer, the poorer varieties being retained for 
local treatment. 
The following analysis, by Mr. F. Claudet, of pyrites from the 
San Domingos mine, may be taken as an average sample of 
.good exported ore : — 
